A topographical analysis of the electrocorticographic DC potential shifts and cortical fluorescence changes was undertaken in both the center and surrounding areas of a penicillin-induced focal epileptic process. A consistent correlation between cortical fluorescence changes and proximity to the center of the focus was not found. Also, a consistent topographical correlation between DC shifts and cortical fluorescence changes was not found. Cortical fluorescence changes were usually of greater amplitude when measured over large vessels than when no major vessels were in the field.